In recent years, in the field of an endoscope, a capsule endoscope having the image capturing function and the radio communication function has appeared. The capsule endoscope is swallowed from the mouth of a subject (human body) for observation (examination) and travels in organs such as the stomach and small intestine (in the body cavity) with the peristaltic movement of the organs while sequentially capturing images by using the image capturing function for an observation period until the capsule endoscope is naturally discharged from the living body of the subject.
Image data captured in the body cavity by the capsule endoscope for the observation period in which the capsule endoscope travels in the organs is sequentially transmitted to the outside of the subject by the radio communication function such as Bluetooth and housed in a memory provided in an external receiving device. By carrying the receiving device having the radio communication function and a memory function, the subject can freely move even in the observation period since the subject swallows the capsule endoscope until the capsule endoscope is discharged. After the observation, a doctor or a nurse performs a diagnosis by displaying images in the body cavity on display means such as a display on the basis of the image data housed in the memory of the receiving device.
Generally, a plurality of antenna elements for receiving image signals transmitted from the capsule endoscope are disposed so as to spread on the outside of the subject, and the receiving device receives image data by selecting one of the antenna elements, with small reception error in the image signals by switching the plurality of antenna elements. Patent Document 1 describes a receiving device for detecting the position of a capsule endoscope in the subject as a transmission source of image signals on the basis of field intensities of antenna elements while switching the antenna elements. The antenna elements are provided with adhesive and are adhered on predetermined regions of the surface of the subject. The antenna element is usually constructed by an antenna body and a coaxial cable bonded and electrically connected to the antenna body.    Patent Document 1: Japanese Patent Application Laid-Open No. 2003-19111